1. Field of the Invention
The present invention relates to a developing agent reproducing, i.e. filtering, hereinafter mostly referred to as "filtering", apparatus for filtering a developing agent (developer) from a mixture of developer and foreign matters, and an image forming apparatus using such developing agent reproducing, i.e. filtering apparatus.
2. Related Background Art
In the past, after a developer image was transferred from an image bearing member to a recording material, residual matters remaining on the image bearing member were removed from the image bearing member by a cleaning blade and the like and such residual matters were disposed as the waste matter. From a view-point of the effective usage of resources, various apparatuses for separating the developing agent from the residual matters and apparatuses for reusing such developing agent have been proposed. Among them, various apparatuses wherein the residual matters are dropped onto a mesh filter to separate the developing agent passed through the filter from the other foreign matter not passed through the filter have been proposed since they have the simple construction.
However, when the developing agent is separated from the other foreign matter by using the filter (particularly, mesh filter) to reproduce the developing agent, there arises a problem that the mesh is clogged by the foreign matter such as paper powder included in the residual matter removed from the image bearing member. In particular, when the mesh is made smaller to remove the smaller foreign matter, the mesh is apt to be clogged. Accordingly, the maintenance of the reproducing, i.e. filtering apparatus must be performed frequently, and, thus, it was difficult to put such filtering apparatus to practical use.
In order to solve this problem, there has been proposed an apparatus wherein a magnetic field is generated by a pair of magnets to eject magnetic toner in the residual matter removed from an image bearing member in a direction opposite to the gravity acting direction where a mesh filter is provided between the pair of magnets to regulate the passage of foreign matter such as paper powder flying together with the magnetic toner through the filter.
By this apparatus, the foreign matter consisting of the non-magnetic matters such as the paper powder regulated by the mesh filter are separated from the magnetic toner, and the separated foreign matter are dropped by their own weight to leave the mesh filter, thereby effectively preventing the clogging of the mesh.
However, when the apparatus is in an inoperative condition for a long time, the triboelectric brush of the magnetic toner (including the foreign matters such as the paper powder) is formed between the pair of magnets. Accordingly, the magnetic toner in the form of the triboelectric brush which was not passed through the mesh filter is adhered to the mesh filter, with the result that, even when the apparatus is operated, such magnetic toner is not separated from the mesh filter, thereby causing the clogging of the mesh.